As electronic components get smaller, lighter and more sophisticated, the semiconductor packaging form is changing from wire bonding type to flip-chip type.
A flip-chip semiconductor apparatus has a configuration in which electrode portions on a substrate are connected to a semiconductor device via bump electrodes. The thus configured semiconductor apparatus suffers from the following problem: When heat is applied as in temperature cycling, the bump electrodes are stressed due to a difference in coefficient of thermal expansion between the substrate made of an organic material such as epoxy resin and the semiconductor device, thus causing the bump electrodes to have defects such as cracking. In order to suppress the occurrence of such defects, it is widely performed to seal gaps between the semiconductor device and the substrate with a sealant called “underfill” to secure them to each other, thereby improving the thermal cycle resistance.
A liquid sealant for use as the underfill is required to be excellent in injection properties, adhesive properties, curing properties, storage stability and the like, and not to generate voids. In addition, a portion sealed with the liquid sealing material is required to be excellent in moisture resistance, thermal cycle resistance, reflow resistance, cracking resistance, warpage resistance and the like.
In order to satisfy the foregoing requirements, an epoxy resin-based material is widely used as the liquid sealing material for use as the underfill.
It is known that controlling the difference in coefficient of thermal expansion between a substrate made of an organic material such as epoxy resin and a semiconductor device and reinforcing bump electrodes by adding a filling material (hereinafter referred to as “filler”) made of an inorganic substance such as a silica filler to a liquid sealing material are effective to improve the moisture resistance and the thermal cycle resistance, in particular the thermal cycle resistance of a portion sealed with the liquid sealing material (see Patent Literature 1).
However, with the recent trend toward narrower gaps (25 to 50 μm) and narrower pitches (up to 150 μm), the thermal cycle resistance is required to be further improved. In addition, the liquid sealing material for use as the underfill is required to also have moisture resistance and is hence required to also have excellent PCT (pressure cooker test) resistance.